added product name uniqueness validation
prevent a product from being destroyed if it belongs to any order
prevent line items from being destroyed in locked orders
added rabl gem
configured rabl to not use root json object
added api v1 base controller
added products api
added net_total and gross_total methods to order
extracted line_items creation to a support module
added .DS_Store to .gitignore
added ! to update_attributes
bug fix on products api spec
bug fixes on order model
added canceled as a locked status
added orders controller, routes and templates to api v1